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Geothermal Heat Storage and Phase Change Materials

Mon, 20 June, 2022

TWI has been working as part of the GeoSmart project to optimise and demonstrate innovations to improve the flexibility and efficiency of geothermal heat and power systems, by combining thermal energy storages with flexible Organic Rankine cycle solutions to provide highly flexible operational capabilities for geothermal installations.

As demand for geothermal energy grows, so there is a need to overcome the challenges of intermittent and unstable power generation performance associated with current geothermal technologies. One solution to provide the guaranteed normal functionality of geothermal power generation systems is the use of phase change materials (PCM).

Finding a stable heat storage medium with excellent heat transfer properties at high temperatures has been important for researchers across the scientific community, particularly for the corrosion behaviour of potential metal/metal-alloy materials applied in thermal energy transfer and storage systems.

High temperature molten salts have become the industry choice for PCMs due to merits including a low vapour pressure, low reactivity in air, and their ability to withstand a high operating temperature. Meanwhile, carbon steels in combination with aluminium are commonly considered as potential metal/metal-alloy materials for service in low temperature sections of geothermal power plants. Irrespective of this, the development of PCMs still encounters the inherent disadvantages associated with the severe corrosion suffered by pipes and vessels at high operating temperatures.

As such, we have been assessing the corrosion behaviour of potential metal/metal-alloy materials through exposure to nitrate-nitrite PCMs at elevated temperatures. These exposure tests involve various electrochemical techniques, with the aim of ranking the suitability of materials for PCM applications.

The aggressiveness of the PCM in relation to the metal/metal-alloy material stability and performance will not only address the limitations associated with higher operating temperatures, but also provide a detailed understanding on the corrosivity of the PCMs and the corrosion resistance of the metal/metal-alloy materials.

You can find out more about the GeoSmart project on the dedicated website and find out about TWI’s materials and corrosion management services here.


The GeoSmart project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 818576.

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